Aligning the Forces - Eliminating the Misalignments in IMU Arrays

Ultra-low-cost single-chip inertial measurement units (IMUs) combined into IMU arrays are opening up new possibilities for inertial sensing. However, to make these systems practical for researchers, a simple calibration procedure that aligns the sensitivity axes of the sensors in the array is needed. In this letter, we suggest a novel mechanical-rotation-rig-free calibration procedure based on blind system identification and a Platonic solid printable by a contemporary 3D-printer. The IMU array is placed inside the Platonic solid and static measurements are taken with the solid subsequently placed on all sides. The recorded data are then used together with a maximum likelihood based approach to estimate the inter-IMU misalignment and the gain, bias, and sensitivity axis non-orthogonality of the accelerometers. The effectiveness of the method is demonstrated with calibration results from an in-house developed IMU array. Matlab-scripts for the parameter estimation and production files for the calibration device (solid) are provided.